Exploring genetic diversity and population structure of the Little Tern (Sternula albifrons) in Taiwan based on mtDNA and ddRAD sequencing data

In this study, Little Tern (Sternula albifrons) populations in Taiwan are examined based on two different types of data: mitochondrial control region DNA sequences and double digest restriction-site associated DNA (ddRAD) sequencing data. Feather samples were collected from 59 chicks across four known breeding colonies located on the eastern (Yilan and Hualien) and western (Penghu and Changhua) coasts of Taiwan. The results obtained are consistent in analyses and do not cluster into two geographical groups with respect to the eastern and western Taiwan. Furthermore, AMOVA analyses and pairwise ΦST/FST estimations based on both types of data reveal little to no differentiation among populations and between groups. The findings of this study suggest high population connectivity among Taiwan’s breeding colonies. Additionally, control region sequences of Taiwan’s Little Terns are compiled with those from Japan deposited in GenBank to compare genetic diversity and examine for phylogeographic breaks that could shape the diversity pattern of the species in eastern Asia. The resulting haplotype network does not clearly separate Taiwanese and Japanese populations, but the three most common haplotypes are prevalent for mainland Japan, Okinawa, and Taiwan. Little Tern populations may be frequently connected, but with some restrictions on gene flow causing moderate to great differentiation among the three. This is further supported by AMOVA analyses, pairwise ΦST estimations, and pattern of positive yet significant isolation by distance.